For automotive applications, fasteners are used to join trim pieces to sections or metal body portions of the automobile. The requirements for these fasteners are that they be insertable into apertures of the automobile and meet standards for both insertion pressure of the insert as well as minimum pullout retention force such that the insert can be removed without damaging the trim piece. Common fastener designs include two or more flexible wings which deflect upon insertion of the fastener and expand by spring force to hold the fastener within an aperture formed in the automobile. A drawback of commonly used fasteners is the inability of the fastener to seal for intrusion of moisture, dust and dirt into the automobile. Another drawback in an all-metal fastener or retainer is that because of the materials used, a plating and/or finish is required to prevent corrosion. Still another drawback of some existing fastener designs is an all metal body of the fastener itself. An all-metal fastener can result in corrosion between the metal contact surfaces of the fastener and the automobile as well as causing damage to the area of the aperture of the automobile upon insertion of the fastener or removal of the fastener.
Some fastener designs have a further drawback by requiring two pieces. In a typical application of a two-piece fastener design, a fastener body or first piece is inserted into an aperture and a second piece is inserted into the first piece to expand the first piece, thus holding the fastener in position. This obviously increases complexity and cost of assembly as well as requiring maintenance of a two part system during vehicle construction.